"jim beam" <
[email protected]> wrote in message
news:
[email protected]...
> * * Chas wrote:
> > "jim beam" <[email protected]> wrote in message
> > news:[email protected]...
> >> * * Chas wrote:
> >>> "Ozark Bicycle" <[email protected]> wrote in
> > message
> >>> news:[email protected]...
> >>>> On May 28, 8:55 pm, "* * Chas" <[email protected]> wrote:
> >>>>> "Ozark Bicycle" <[email protected]> wrote in
> >>> message
> >>>>> news:[email protected]...
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>> On May 28, 2:06 am, Morten Reippuert Knudsen<[email protected]>
> >>> wrote:
> >>>>>>> Michael Press <[email protected]> wrote:
> >>>>>>>> In article
> >>>>>>>> <[email protected]>
> >>>>>>>> ,
> >>>>>>>> Ozark Bicycle
> >>>>>>>> <[email protected]> wrote:
> >>>>>>>>> When did MA-2s become great????
> >>>>>>>> With the MA-40, and simultaneous disappearance of all
> >>>>>>>> box-section, fully socketed, plugged seam, non-anodized,
> >>>>>>>> unmachined sidewall rims.
> >>>>>>> I belive that Ambrosio still has an item:
> >>>>>>> <http://www.ambrosiospa.com/provajpg/pag110.htm>
> >>>>>> Note that the "Durex" (hard anodized) version is only available
in
> >>>>>> 36H. Hmmmmm....
> >>>>> That's the only rim I've seen with cracking around the eyelets.
> >>>>>
> >>>> That being the Ambrosio Nexus 36H "Durex"?
> >>>>
> >>> Nope, Ambrosio 19 Extra "Durex" gray anodized. I bought them from a
> >>> friend about 20 years ago. He ran a shop and built them for himself.
> > Campy
> >>> Record hubs, DT spokes. Specialized 700c x 25 (really about 18 or
> > 19mm)
> >>> tires, very well made wheels.
> >>>
> >>> I only used them on smooth roads and easy rides until last year when
I
> >>> started riding them after work. One of the bike trails I rode a lot
> > had
> >>> several sections where the pavement was uplifted from tree roots. I
> > hit
> >>> these a few times in the dark hauling butt to get home.
> >>>
> >>> I noticed that the rear spokes where coming loose after every ride
> > then I
> >>> saw the cracks in the anodizing and the bulging spoke eyelets.
> >>>
> >>> Aside from cheap old sewup rims without eyelets and Fiame yellow
label
> >>> rims, I'd never seen spoke hole problems.
> >>>
> >>> Chas.
> >>>
> >>>
> >>>
> >> what was the spoke tension?
> >
> > When I first started riding them the tension was very tight but even.
>
> but if you can't quote a tension, we have to assume you didn't use a
> tensiometer - and that's the problem. evenness makes no difference to
> tension magnitude.
>
> > These rims are supposed to have a bad reputation for cracking.
>
> this reputation must be from those that build with excess tension.
>
> > I think
> > that it was the shock from hitting the root bumps that caused the
problem.
>
> radial loading reduces spoke tension, not increases it. it's simply
> fatigue loading and being too close to yield that is the problem.
>
> >
> > I've been building wheels for 30+ years and never saw a spoke break or
a
> > rim crack on any wheel that I built. I never used any kind of
lubricant on
> > the nipples, I judged tightness by feel and kept runout to under.010
> > overall (closer with better rims).
>
> but you said your friend built them not yourself! and you don't know
> the spoke tension. runout has /nothing/ to do with spoke tension unless
> the rim is about to buckle - and if you're at that limit, tension is
> already /way/ too high.
>
> bottom line, you say the eyelets were bulging. that is incontrovertibly
> excess spoke tension - any rim will crack with spoke tension high enough
> to cause that.
Hey Jim, for over a hundred years millions of bike wheels have been built
without the benefit of tensionometers.
The only spokes that I ever broke were on Bike Boom clunkers back in the
1970s. I've bent a few rims - I hit the back of a stopped car at 30+ mph,
I skidded sideways into a curb and I pacman'd a rim in a sewer grate.
I can appreciate the benefits of using a tensionometer on a highly
stressed low spoke count wheel. I ride mostly 36 spoke wheels with a few
32 spoke wheels I've picked up along the way.
I considered buying a tensionometer several times then I laid down by
myself until the feeling passed. I figured that I'd just drive myself nuts
retensioning and retruing about 20 sets of wheels. My wheels stay true and
I rarely have to adjust any of them.
I'm still riding this Ambrosio rim for short rides on flat, smooth bike
trails. I want to watch the progress of the cracking. I've stopped
adjusting the wheel and the spokes don't feel any the worse - i.e.. they
haven't loosened any more.
As far as who built these wheels and how, they were the most accurate
wheels I've ever used and they stayed true until I hit a number of 2"-4"
high root bumps in the pavement in the dim light of dusk. The impacts
almost knocked me off of the bike.
In trying to find a retro replacement Ambrosio rim, Google searching came
up with a number of reports and complaints about this model rim being
prone to cracking. I would expect this from a 20+ year old rim that was an
early design.
Chas.